selenium之python源码解读-expected_conditions

一、expected_conditions

之前在 selenium之python源码解读-WebDriverWait 中说到，until方法中method参数，需要传入一个function对象，如果每次都自定义或者使用lambda函数，显得比较麻烦。

其实在expected_conditions中，Selenium提供了一些常用的元素查找的条件类

在selenium\webdriver\support\expected_conditions.py中定义的所有类如下：

class title_contains(object):
class presence_of_element_located(object):
class visibility_of_element_located(object):
class visibility_of(object):
class presence_of_all_elements_located(object):
class visibility_of_any_elements_located(object):
class visibility_of_all_elements_located(object):
class text_to_be_present_in_element(object):
class text_to_be_present_in_element_value(object):
class frame_to_be_available_and_switch_to_it(object):
class invisibility_of_element_located(object):
class element_to_be_clickable(object):
class staleness_of(object):
class element_to_be_selected(object):
class element_located_to_be_selected(object):
class element_selection_state_to_be(object):
class element_located_selection_state_to_be(object):
class number_of_windows_to_be(object):
class new_window_is_opened(object):
class alert_is_present(object):

在上面定义的类中都实现了 __call__(self, driver)方法，这就意味着该类的对象是一个可调用的对象

如以visibility_of_element_located类为例：

实例化一个对象：visibility_of_element_located(locator)

在对象后加()：调用对象，即调用类的 __call__方法，visibility_of_element_located(locator)(driver)

二、类中的 __init__  和__call__方法传参总结

1、传入locator，和driver参数

def __init__(self, locator):
　　self.locator = locator

def __call__(self, driver):
　　return _find_element(driver, self.locator)

而locator，需要传入一个iterateble对象，如tuple，(by.ID,"id")

def _find_element(driver, by):
    """Looks up an element. Logs and re-raises ``WebDriverException``
    if thrown."""
    try:
        return driver.find_element(*by)
    except NoSuchElementException as e:
        raise e
    except WebDriverException as e:
        raise e

2、传入element，和ignored参数

def __init__(self, element):
    self.element = element

def __call__(self, ignored):
    return _element_if_visible(self.element)

该类型的传参有4个

class visibility_of(object)

class staleness_of(object)

class element_located_to_be_selected(object)

class element_selection_state_to_be(object)

lement_located_to_be_selected(object)和element_selection_state_to_be(object)实现的功能是一样的

3、其他还有title、window、handler、alert此处不再一一例举，具体查看源码